喀斯特山区不同土地利用方式下石灰土化学风化特性

Chemical weathering characteristics of calcareous soil under different land-use patterns in a Karst mountainous area

研究喀斯特山区不同土地利用方式(耕地、荒草地、退耕还草地和林草间作地)石灰土剖面化学风化特征,探讨矿质元素在石灰土剖面的分布、迁移和富集特征,从不同土地利用方式下土壤风化度,元素淋溶度、迁移度和残积度的角度分析土壤化学风化特征。结果表明:喀斯特山区石灰土剖面氧化物含量以SiO2、Al2O3、Fe2O3为主,其他氧化物含量相对较低,均属于中等变异元素,SiO2、Al2O3、MgO含量以荒草地较高,CaO、Na2O含量以林草间作地较高,Fe2O3、MnO、P2O5、K2O以耕地较高;研究区土壤处于中等化学风化阶段,富铝化程度弱,不同土地利用方式下荒草地土壤化学蚀变系数较强,林草间作地土壤富铝化程度较高;研究区土壤K、Na、Ca淋失严重,荒草地盐基离子淋失明显,林草间作地盐基离子淋失程度相对较低;土壤Fe、Al相对富集明显,残积程度高,林草间作地Al含量积累明显,退耕还草地Fe含量富集显著;实施“退耕—还草”等增加植被覆盖度的治理模式对土壤的保护作用显著。

We determined the chemical weathering characteristics of calcareous soil profiles under different land-use patterns[cultivated land(CL),wild grassland(WGL),returning farmland to grassland(RFL)and forest and grass intercropping(FGL)]in the Karst mountainous area.The distribution,migration,and enrichment of mineral elements in calcareous soil profiles were analyzed,and the chemical weathering characteristics of soil under different land-use patterns were determined by measuring the soil weathering degree,element leaching degree,migration degree,and residual degree.It was found that the main oxides in the limestone profile in the Karst mountainous area were SiO2,Al2O3,and Fe2O3,with smaller amounts of other oxides(medium-variable elements).Comparing soils from areas with different land-use patterns,WGL soil was richer in SiO2,Al2O3,and MgO;FGL soil was richer in CaO and Na2O;and CL soil was richer in Fe2O3,MnO,P2O5 and K2O.The soil in the study area was in the middle chemical weathering stage,with a weak degree of aluminization.The chemical alteration coefficient of the soil in desert grassland was stronger under certain land-use patterns.Aluminization was strongest in FGL soil.Leaching of soil K,Na,and Ca was severe in the study area,and leaching of salt ions was more obvious in barren grasslands.The strength of leaching of salt ions was relatively low in FGL soil.Soils had relatively high Fe and Al contents,especially Al in FGL soil and Fe in RFL soil.The implementation of governance models such as returning farmland to grassland to increase vegetation cover will significantly affect soil protection.These findings provide a scientific basis and theoretical guidance for understanding the formation and evolution of lime soil in the Karst mountainous area,soil degradation mechanisms,soil management and land-use countermeasures,ecological restoration,and soil and water conservation in ecologically vulnerable Karst areas.